How to move a cube on a plane
Helpful tricks to use when moving/scaling/rotating an object: to move on two axes while scaling/moving/rotating press S/G/R then SHFT+(axis you don't want to transform on). This will allow you to move on, say both X+Y axes, but not the Z axis if you press G-SHFT+Z, or only scale on X and Z- S-SHFT+Y.